diff --git a/DataStorage/Database/Connection/SQLiteConnection.php b/DataStorage/Database/Connection/SQLiteConnection.php
index dd4df8a5d..7362d2248 100644
--- a/DataStorage/Database/Connection/SQLiteConnection.php
+++ b/DataStorage/Database/Connection/SQLiteConnection.php
@@ -51,7 +51,7 @@ class SqliteConnection extends ConnectionAbstract
     /**
      * {@inheritdoc}
      */
-    public function connect(array $dbdata = null)
+    public function connect(array $dbdata = null) : void
     {
         $this->close();
 
diff --git a/DataStorage/Session/ConsoleSession.php b/DataStorage/Session/ConsoleSession.php
index a37e4225d..f26474b8b 100644
--- a/DataStorage/Session/ConsoleSession.php
+++ b/DataStorage/Session/ConsoleSession.php
@@ -28,7 +28,7 @@ class ConsoleSession implements SessionInterface
     /**
      * Session ID.
      *
-     * @var string|int
+     * @var string|int|null
      * @since 1.0.0
      */
     private $sid = null;
@@ -36,13 +36,13 @@ class ConsoleSession implements SessionInterface
     /**
      * Constructor.
      *
-     * @param string|int|bool $sid Session id
+     * @param string|int|null $sid Session id
      *
      * @since  1.0.0
      */
-    public function __construct($sid = false)
+    public function __construct($sid = null)
     {
-        if ($sid !== false) {
+        if ($sid !== null) {
             $this->sid = $sid;
         }
     }
@@ -89,14 +89,14 @@ class ConsoleSession implements SessionInterface
     /**
      * {@inheritdoc}
      */
-    public function save()
+    public function save() : void
     {
     }
 
     /**
      * {@inheritdoc}
      */
-    public function lock()
+    public function lock() : void
     {
     }
 }
diff --git a/DataStorage/Session/SocketSession.php b/DataStorage/Session/SocketSession.php
index b24b816a3..966e48677 100644
--- a/DataStorage/Session/SocketSession.php
+++ b/DataStorage/Session/SocketSession.php
@@ -36,13 +36,13 @@ class SocketSession implements SessionInterface
     /**
      * Constructor.
      *
-     * @param string|int|bool $sid Session id
+     * @param string|int|null $sid Session id
      *
      * @since  1.0.0
      */
-    public function __construct($sid = false)
+    public function __construct($sid = null)
     {
-        if ($sid !== false) {
+        if ($sid !== null) {
             $this->sid = $sid;
         }
     }
@@ -96,7 +96,7 @@ class SocketSession implements SessionInterface
     /**
      * {@inheritdoc}
      */
-    public function lock()
+    public function lock() : void
     {
     }
 }
diff --git a/Socket/Client/Client.php b/Socket/Client/Client.php
index bcce8afd6..5a9246307 100644
--- a/Socket/Client/Client.php
+++ b/Socket/Client/Client.php
@@ -59,7 +59,7 @@ class Client extends SocketAbstract
     /**
      * {@inheritdoc}
      */
-    public function create(string $ip, int $port)
+    public function create(string $ip, int $port) : void
     {
         parent::create($ip, $port);
     }
@@ -67,7 +67,7 @@ class Client extends SocketAbstract
     /**
      * {@inheritdoc}
      */
-    public function run()
+    public function run() : void
     {
         socket_connect($this->sock, $this->ip, $this->port);
         $i = 0;
@@ -113,7 +113,7 @@ class Client extends SocketAbstract
     /**
      * {@inheritdoc}
      */
-    public function close()
+    public function close() : void
     {
         parent::close();
     }
diff --git a/Socket/Server/Server.php b/Socket/Server/Server.php
index 64e5c5cb6..84eca9a2d 100644
--- a/Socket/Server/Server.php
+++ b/Socket/Server/Server.php
@@ -103,7 +103,7 @@ class Server extends SocketAbstract
     /**
      * {@inheritdoc}
      */
-    public function create(string $ip, int $port)
+    public function create(string $ip, int $port) : void
     {
         $this->app->logger->info('Creating socket...');
         parent::create($ip, $port);
@@ -125,7 +125,7 @@ class Server extends SocketAbstract
         $this->limit = $limit;
     }
 
-    public function handshake($client, $headers)
+    public function handshake($client, $headers) : bool
     {
         // todo: different handshake for normal tcp connection
         return true;
@@ -173,7 +173,7 @@ class Server extends SocketAbstract
     /**
      * {@inheritdoc}
      */
-    public function run()
+    public function run() : void
     {
         $this->app->logger->info('Start listening...');
         socket_listen($this->sock);
@@ -220,7 +220,7 @@ class Server extends SocketAbstract
         $this->close();
     }
 
-    public function connectClient($socket)
+    public function connectClient($socket) : void
     {
         $this->app->logger->debug('Connecting client...');
         $this->clientManager->add($client = new ClientConnection(uniqid(), $socket));
@@ -228,7 +228,7 @@ class Server extends SocketAbstract
         $this->app->logger->debug('Connected client.');
     }
 
-    public function disconnectClient($client)
+    public function disconnectClient($client) : void
     {
         $this->app->logger->debug('Disconnecting client...');
         $client->setConnected(false);
@@ -247,7 +247,7 @@ class Server extends SocketAbstract
     /**
      * {@inheritdoc}
      */
-    public function close()
+    public function close() : void
     {
         parent::close();
     }
@@ -260,7 +260,7 @@ class Server extends SocketAbstract
         parent::__destruct();
     }
 
-    private function unmask($payload)
+    private function unmask($payload) : string
     {
         $length = ord($payload[1]) & 127;
         if ($length == 126) {
diff --git a/Socket/SocketAbstract.php b/Socket/SocketAbstract.php
index d5d5e040f..94ec44c3d 100644
--- a/Socket/SocketAbstract.php
+++ b/Socket/SocketAbstract.php
@@ -60,7 +60,7 @@ abstract class SocketAbstract implements SocketInterface
     /**
      * {@inheritdoc}
      */
-    public function create(string $ip, int $port)
+    public function create(string $ip, int $port) : void
     {
         $this->ip   = $ip;
         $this->port = $port;
@@ -82,7 +82,7 @@ abstract class SocketAbstract implements SocketInterface
     /**
      * {@inheritdoc}
      */
-    public function close()
+    public function close() : void
     {
         if ($this->sock !== null) {
             socket_shutdown($this->sock, 2);
diff --git a/Socket/SocketInterface.php b/Socket/SocketInterface.php
index ef095cad0..e1e759d06 100644
--- a/Socket/SocketInterface.php
+++ b/Socket/SocketInterface.php
@@ -30,10 +30,12 @@ interface SocketInterface
      *
      * @param string $ip   IP address
      * @param int    $port Port
+     * 
+     * @return void
      *
      * @since    1.0.0
      */
-    public function create(string $ip, int $port);
+    public function create(string $ip, int $port) : void;
 
     /**
      * Close socket.